Can confirm, have the same problem: server loses connection after a while with no usable log entries except for the avahi-daemon message.
I am however not using Ubuntu, but Arch. Also not in a VM.
The NIC is for me the same: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 02).
Can confirm, have the same problem: server loses connection after a while with no usable log entries except for the avahi-daemon message.
I am however not using Ubuntu, but Arch. Also not in a VM.
The NIC is for me the same: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 02).